The present invention relates to a drum cleaning apparatus for cleaning drums of printing presses.
Printing presses are classified into three types: platen, cylinder, and rotary. Platen presses are the simplest. They are used for low volume operations. Platen presses essentially consist of two plates; one plate is the printing surface which holds the type, and the other plate is the impression surface which holds the paper. Cylinder presses are used in medium volume operations. They have a flat inked printing surface, but the impression surface is a cylinder. The printing surface rests on a bed that moves back and forth under the inking rollers. The impression cylinder rotates in coordination with motion of the printing surface. When the printing surface bed moves into contact with the impression cylinder, a print is produced. When the printing surface bed is out of contact with the impression cylinder, the printed sheet is removed and an unprinted sheet is positioned for the next cycle.
Rotary presses, which are used in high volume operations, use a cylindrical impression surface and a cylindrical printing surface. Both cylinders rotate in contact with each other as the paper passes between them to produce a print. The cylindrical printing surface (also known as a plate cylinder) is inked by ink rollers as the cylinder rotates.
While a printing press operates, paper fibers separate from the paper and adhere to the drum surface as do dried ink and other contaminants. After every press run, and periodically during a long press run, the cylindrical drums are cleaned of contaminants.
In the conventional type of drum cleaning apparatus for a printing press, as described in Japanese Utility Model Publication No. 36924/1992, a cleaning head made of a resilient material such as sponge presses a cleaning sheet against the surface of a drum in a printing press. The cleaning sheet is moved contrary to the rotational direction of the drum to rub and clean the surface of the drum of contaminants. The cleaning head is slender and rod-like along the axial direction of the drum. The cleaning head is attached to a supporting body which is moved against and away from the drum during the cleaning process.
In the conventional type of drum cleaning apparatus, however, used for cleaning the plate cylinder or impression cylinder of a rotary printing press used for printing newspapers, problems arise if the cylinder is too wide. If the cylinder width is increased to around 1.7m., the length of the cleaning head becomes correspondingly longer in proportion to its width with a concomitant increase in the normal stress of the cleaning head. The resulting deformation makes it difficult to press the cleaning sheet against the drum evenly and with an even pressure. Uneven cleaning is often the effect.